Our 2003 GMC 2500 Duramax Allison Transmission pickup seems

Resolved Question:

Our 2003 GMC 2500 Duramax Allison Transmission pickup seems to have slack when we come to a complete stop and sometimes we feel it the second we start to pull forward after being stopped. It seems like it is in the brakes or transmission. We have had the transmission checked because we were told that there is a braking system within the transmission. After $1600 work on the transmission, the problem persists. Do you have a suggestion.

This bulletin is being revised to change the automatic transmission fluid to use from DEXRON®-III to DEXRON®-VI and change the Warranty Labor Time information. Please discard Corporate Bulletin Number 03-07-30-011D (Section 07 -- Transmission/Transaxle).

Use the service procedure shown below to access and change the torque converter relief spring and lube regulator spring in the front support assembly. Installation of these parts will not eliminate the torque converter bleed down or a potential delayed engagement. These parts will prevent transmission DTCs and their resulting default actions associated with an extended period of non-usage.

Important:

•

A vented transmission fluid level indicator, P/N 15115171, should be installed after the transmission has been reinstalled. This vented indicator will help to prevent fluid leaks out of the vent in cold weather operation. For additional information on this vented transmission fluid indicator, refer to Corporate Bulletin Number 03-07-30-054 (SI Document ID #1397788).

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After completing this modification, the transmission control module (TCM) shift adapts must be relearned for proper transmission operation. Follow the procedure outlined in Corporate Bulletin Number 02-07-30-032A (SI Document ID #1198957) to quickly relearn the transmission shift adapts. Note that the fast learn procedure is not available for 2001 model year vehicles.

Caution:

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The Allison® 1000 Series (M74) transmission has a dry weight of approximately 150 kg (330 lbs). The torque converter has a dry weight of approximately 29 kg (63 lbs).

•

Use caution when removing, installing, servicing or moving the transmission in order to prevent personal injury.

•

Get assistance when lifting the transmission. A hoist is the preferred lifting device. Ensure that the lifting device is adequate to support the transmission.

Remove the transmission from the vehicle. For transmission removal, refer to the proper Service Information Document listed below. After removal, return to this document for the transmission modification procedure.

•

For vehicles equipped with the DuramaxTM Diesel (LB7), refer to Document ID #758397.

Important: You will need to note the proper orientation of the two springs and the two valves. The replacement springs must be installed exactly like the removed component or transmission failures and/or shift conditions will occur.

With the ground sleeve facing up and the support assembly turned so the area without visible oil passages is on the top right, a notch should be seen at the upper left portion of the support assembly. With the aid of the J 43773 (2), compress the lube regulator spring to enable removal of the retaining pin (1). The following items are to be removed.

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The retaining pin

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The stop (4) with O-ring seal (3) (remove and discard the O-ring seal)

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A short spring (2)

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The lube regulator valve (1)

Insert the J 43773 (2) into the bore you just removed the above components from. Compress the converter relief valve spring enough to remove the "U" shaped retaining clip (1) and remove the clip. Then remove the following items.

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The converter relief spring (2)

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The converter relief valve (1)

Notice: Transmission damage may occur when springs and other parts are mistakenly interchanged. Proper springs and other part identification is very important.

Position the support assembly so that the converter relief valve/lube regulator bore is facing upward. Then install the following components.

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The converter relief valve (1) (big end first, the small end fits into the converter relief spring)

Important: If the lube regulator stop O-ring seal is cut or omitted, the transmission will not prime.

Install a new O-ring seal (3) on the lube regulator spring stop (4). Dip the lube regulator spring stop in transmission fluid. Install the stop into the bore. Use the J 43773 tool to compress the spring. Install the retaining pin. Ensure that the pin is below the surface of the support and the stop is positioned against the stop pin.

A vented transmission fluid level indicator, P/N 15115171, should be installed after the transmission has been reinstalled. This vented indicator will help to prevent fluid leaks out of the vent in cold weather operation.

•

After completing this modification, the transmission control module (TCM) shift adapts must be relearned for proper transmission operation. Follow the procedure outlined in Corporate Bulletin Number 02-07-30-032 to quickly relearn the transmission shift adapts. Note that the fast learn procedure is not available for 2001 model year vehicles.

For transmission installation procedures, refer to the proper Service Information Document listed below.

•

For vehicles equipped with the DuramaxTM Diesel (LB7), refer to Document ID #758397.

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